讓 Jev 學會煞車：從被冷落的 Reposition 到 17 秒通關的戰術調校

// 舊版實作：evade 與 reposition 共用相同的 24 方位逃逸分支
if (reflex || maneuver === 'evade' || maneuver === 'reposition') {
  // 24 方位候選落點取樣 ...
}

snapshot(sequence: number): FlightSnapshot {
  const round = (n: number) => Math.round(n * 10) / 10;
  const asteroids = this.rocks.map(r => {
    const d = delta(this.ship, r), dist = length(d);
    // ...
    return {
      id: r.id,
      distance: round(dist),
      bearing: round(angleDifference(Math.atan2(d.y, d.x), this.ship.angle) * 180 / Math.PI),
      // 關鍵新增：包含移動目標動態前置量的真實瞄準夾角
      leadBearing: round(angleDifference(leadAngle(this.ship, r), this.ship.angle) * 180 / Math.PI),
      radius: r.radius,
      closingSpeed: round(-dot / (dist || 1)),
      closestApproach: round(Math.hypot(d.x + v.x * t, d.y + v.y * t) - r.radius - SHIP_RADIUS),
      secondsToClosest: round(t),
    };
  }).sort((a, b) => a.distance - b.distance).slice(0, 10);

  const inRange = asteroids.filter(r => r.distance < 580);
  return {
    sequence,
    wave: this.wave,
    lives: this.lives,
    ship: {
      speed: round(Math.hypot(this.ship.vx, this.ship.vy)),
      heading: round(wrap(this.ship.angle * 180 / Math.PI, 360)),
      invulnerable: this.ship.shield > 0,
    },
    // 戰術衍生特徵
    tactics: {
      // 1. 全場即將在 0.8 秒內闖入安全包絡線的急迫威脅總數
      imminentThreats: this.rocks.filter(r => imminentThreat(this.ship, r)).length,
      // 2. 當前船頭已對齊前置角且在射程內的有效射擊機會數
      firingOpportunities: this.rocks.filter(r => canFireAt(this.ship, r)).length,
      // 3. 射程內所有候選隕石中，最小的絕對瞄準偏差角（度）
      bestAimError: inRange.length ? Math.min(...inRange.map(r => Math.abs(r.leadBearing))) : null,
    },
    asteroids,
  };
}

export function questionsFor(snapshot: FlightSnapshot) {
  // ...
  return {
    maneuver: choice(
      'Choose the most useful maneuver for the next roughly 1.2 seconds in Asteroids. Survive and destroy rocks. Units are pixels, pixels/second, degrees, seconds. Bearing 0 is ahead; negative is left. leadBearing includes moving-target lead. `tactics.imminentThreats` counts asteroids entering a safety envelope within 0.8 seconds across the whole field. `tactics.firingOpportunities` counts currently aligned in-range shots across the whole field. `tactics.bestAimError` is the smallest absolute leadBearing among in-range radar candidates, or null if none are in range. First consider immediate danger: evade takes priority over preparing an attack. With no immediate danger, consider whether to prepare or attack: speed above about 180 or no aligned shots with bestAimError above about 45 degrees favors reposition. At controlled speed with a useful firing angle, intercept; distant targets alone favor approaching with intercept, not reposition. Negative closestApproach predicts overlap at constant velocity over up to 5 seconds, not necessarily immediate danger. secondsToClosest=0 may describe a receding rock; positive closingSpeed means approaching. A local reflex handles emergencies in every maneuver. Shield is temporary.',
      {
        intercept: 'Attack from a usable firing angle at controlled speed, or close the distance to out-of-range targets. Lead shots and approach when appropriate.',
        evade: 'Escape an imminent collision indicated by tactics.imminentThreats or a clear approaching near-term threat. Accelerate toward a clear endpoint. High ship speed alone is NOT a reason to evade when threats are absent and asteroids are receding or well separated; use reposition to brake in that situation.',
        reposition: 'No imminent threat, but the ship is drifting too fast (roughly above 180 px/s) OR needs a large turn to get a shot. Even if a shot is currently aligned, excessive safe drift is a reason to reposition. Counter-thrust to reduce speed, then coast and aim without accelerating toward the target. Fire opportunistically. This is preparation and braking, not emergency escape.',
      }
    ),
    target: choice(
      'Independently choose the most useful asteroid to aim at if intercept or reposition is selected. Prefer a nearby target with a small absolute leadBearing or a closing threat that can be destroyed. Reposition can first brake before aiming. Use none if no useful target exists. This answer cannot see the maneuver answer.',
      targets
    ),
  };
}

export function steer(game: Game, maneuver: Maneuver, targetId: string | null): PilotOutput {
  const ship = game.ship;
  let target = game.rocks.find(r => r.id === targetId);
  if (!target) target = [...game.rocks].sort((a, b) => length(delta(ship, a)) - length(delta(ship, b)))[0];
  if (!target) return { controls: IDLE, reflex: false, target: null };

  const reflex = game.rocks.some(r => imminentThreat(ship, r));
  let desired: number, thrust = false;

  if (reflex || maneuver === 'evade') {
    // 1. 規避分支：24 方位候選落點取樣，尋找空間淨距最大方向加速脫離
    let best = -Infinity; desired = ship.angle;
    for (let i = 0; i < 24; i++) {
      const a = i * Math.PI / 12;
      const point = { x: ship.x + ship.vx * 0.45 + Math.cos(a) * 180, y: ship.y + ship.vy * 0.45 + Math.sin(a) * 180 };
      const clearance = Math.min(...game.rocks.map(r => length(delta(point, { x: r.x + r.vx * 0.7, y: r.y + r.vy * 0.7 })) - r.radius));
      const value = clearance - Math.abs(angleDifference(a, ship.angle)) * 28;
      if (value > best) { best = value; desired = a; }
    }
    thrust = Math.abs(angleDifference(desired, ship.angle)) < 0.75;
  } else if (maneuver === 'reposition') {
    // 2. 重新佔位分支：逆向噴射減速，隨後慣性滑行鎖定目標射角
    if (Math.hypot(ship.vx, ship.vy) > 120) {
      // 階段 1：航速超過 120 px/s，瞄準速度向量的反方向 (-vx, -vy)
      desired = Math.atan2(-ship.vy, -ship.vx);
      // 嚴格等待船頭完全轉到反方向（誤差小於 0.35 徑度 / 約 20 度）才點火反推！
      thrust = Math.abs(angleDifference(desired, ship.angle)) < 0.35;
    } else {
      // 階段 2：航速已受控 (< 120 px/s)，關閉推進器，船頭轉向目標移動前置角
      desired = leadAngle(ship, target);
      thrust = false;
    }
  } else {
    // 3. 截擊分支：對準目標前置角，距離遠且未超速時加速進逼
    desired = leadAngle(ship, target);
    thrust = length(delta(ship, target)) > 260 && Math.hypot(ship.vx, ship.vy) < 170
      && Math.abs(angleDifference(desired, ship.angle)) < 0.45;
  }

  const error = angleDifference(desired, ship.angle);
  // 全域伺機開火：船頭對齊任何一顆隕石的預估前置角且通過 0.15s 冷卻即擊發
  const fire = game.rocks.some(r => canFireAt(ship, r));
  return { controls: { turn: Math.max(-1, Math.min(1, error * 3.5)), thrust, fire }, reflex, target: target.id };
}

const cases = [
  { name: '受控速度下的開闊正面目標', expected: 'intercept', speed: 0, heading: 0, distance: 300, rockVx: 0 },
  { name: '背向目標高速漂移（需煞車）', expected: 'reposition', speed: 260, heading: Math.PI, distance: -300, rockVx: 0 },
  { name: '空域安全但目標全在身後（偏差角 180°）', expected: 'reposition', speed: 0, heading: Math.PI, distance: 300, rockVx: 0 },
  { name: '即將迎面撞上的急迫隕石', expected: 'evade', speed: 0, heading: 0, distance: 60, rockVx: -100 },
];

npm run test:jev

{"scenario":"受控速度下的開闊正面目標","expected":"intercept","matched":true,"probabilities":{"intercept":0.89,"evade":0.06,"reposition":0.05},"latencyMs":326}
{"scenario":"背向目標高速漂移（需煞車）","expected":"reposition","matched":true,"probabilities":{"reposition":0.52,"evade":0.34,"intercept":0.14},"latencyMs":172}
{"scenario":"空域安全但目標全在身後（偏差角 180°）","expected":"reposition","matched":true,"probabilities":{"reposition":0.68,"intercept":0.16,"evade":0.16},"latencyMs":129}
{"scenario":"即將迎面撞上的急迫隕石","expected":"evade","matched":true,"probabilities":{"evade":0.97,"intercept":0.03,"reposition":0.00},"latencyMs":143}